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I have ti046b1 chip (Serial I2C F-RAM) to read.

I tried to read it with my raspberry Pi 3, so I connected SDA SCL VDD GND as shown in pictures, but when I run the command "i2cdetect -y 1" on my Raspberry it shows no device connected to I2C interface (empty) like that:

pi@raspberrypi:~ $ i2cdetect -y 1

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f

00:          -- -- -- -- -- -- -- -- -- -- -- -- --

10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

70: -- -- -- -- -- -- -- --

do you have any idea to solve that ?

  • I tried by inverting (swiping) SDA SLC connections

  • I tried by pulling-up to 3.3V SDA and SCL with 10k resistors (as stated here) to end-up with 1.5K pull-up resistance

  • I checked that there are a built in pull-up 1.8K resistors in the raspberry 3 (see the ohmmeter measure with Pi powerd off of course :) )

  • I tried to change I2C baudrate by the command:

    sudo modprobe -r i2c_bcm2708

    sudo modprobe i2c_bcm2708 baudrate=100000

tested with 100KHZ, 200KHZ, 400KHZ, 800KHZ, 1200KHZ (the result is the same

  • I have put a scope probes on SCL and SDA when the printer is powered on to see how it negociate (see the piture below)

could you please help me to solve that ?

And to anticipate your first question : I checked all the connections for this wiring :)

scope probes on SCL and SDA when the printer is powered with the chip is inside Scope probes on SDA SCL Circuit Chip and schematic Existing pi 3 built-in pull-up 1.8K proven (pi is not powered) internal Pull-Up resistor i2cdetect response

I2C is enabled

Wiring to my Raspberry Pi 3

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    Are you sure it's a 3V3 device? Have you a datasheet link? You SHOULD NOT use additional pull-ups (SDA/SCL already have hard pull-ups on the Pi). – joan Dec 7 '18 at 14:37
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    Those joints look a little sketchy. – goldilocks♦ Dec 7 '18 at 16:32
  • Yes I am sure: this chip is a printer chip, so I connected a voltmeter to it when the chip is inside the printer, and the voltage is 3V3 when it is powered by the printer – Me TI Dec 8 '18 at 14:38
  • Yes I admet that the joints are sketchy :) but the continuity is ensured – Me TI Dec 8 '18 at 15:17
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have you enabled the I2C interface? enter image description here

enter image description here

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    i2cdetect throws an error if the bus isn't already enabled. – goldilocks♦ Dec 7 '18 at 16:24
  • yes it is enabeled by the command: sudo raspi-config and the command ls /dev/*i2c* answers by : /dev/i2c-1 – Me TI Dec 8 '18 at 14:39
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You missed the required pullups, there aren't any provisioned on the host GPIO (because I²C is only one of the possible functions of these two GPIOs) and your device does not have them either.

But you need them, about 3.3kΩ from SDA to +3.3V and another 3.3kΩ from SCL to +3.3V.

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  • The Pi has 1.8kΩ pullups on board. – Milliways Dec 8 '18 at 23:57
  • No ! there is already a built in pull-up 1.8k resistor in the raspberry pi 3 between SDA-3.3V and SCL-3.3V (I have measured that for you, see the picture) – Me TI Dec 9 '18 at 11:41
  • Well, no clue then. – Janka Dec 9 '18 at 13:06
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Looks like other people over on EEVBlog forums have been trying to reverse-engineer this printer cartridge chip and have had some success. If they are correct then it uses 10-bit addressing so i2cdetect will not find it as it only scans the 7-bit address space. Strangely there's someone asking a similar question to yours on that forum too...

Also, from the same discussion, some people are suggesting that this chip is not FRAM memory but actually a re-badged processor with hardware AES pretending to be a FRAM chip.

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